Many crocodilians survived the mass extinction that wiped out almost all of the dinosaurs 66 million years ago, but only 23 species survive today, six of which are classified by the International Union for Conservation of Nature as critically endangered and a further four classified as either endangered or vulnerable.

“Millions of years ago these creatures and their now extinct relatives thrived in a range of environments that ranged from the tropics, to northern latitudes and even deep in the ocean. However, all this changed because of changes in the climate, and crocodylians retreated to the warmer parts of the world,” Mannion said.

Crocodylians are ectotherms, meaning they rely on external heat sources from the environment such as the Sun.

In this study, researchers compiled a dataset of the entire known fossil record of crocodylians and their extinct relatives and analysed data about Earth’s ancient climate.

They wanted to explore how the group responded to past shifts in climate, to better understand how the reptiles may cope in the future.

The researchers concluded that at higher latitudes in areas we now know as Europe and America, declining temperatures had a major impact on crocodylians and their relatives.

At lower latitudes the decline of crocodylians was caused by areas on many continents becoming increasingly arid.

For example, in Africa around ten million years ago, the Sahara desert was forming, replacing the vast lush wetlands in which crocodylians thrived.

In the future, the team suggest that a warming world caused by global climate change may favour crocodylian diversification again, but human activity will continue to have a major impact on their habitats.